A young (31day old) red tree vole (Arborimus longicaudus) eating a Douglas fir needle. Red tree voles are rarely seen. They are nocturnal and live in Douglas fir tree tops and almost never come to the forest floor. They are one of the few animals that can persist on a diet of conifer needles which is their principle food. As a defense mechanism, conifer trees have resin ducts in their needles that contain chemical compounds (terpenoids) that make them unpalatable to animals. Tree voles, however, are able to strip away these resin ducts and eat the remaining portion of the conifer needle.